1. Field of the Invention
The present invention relates to a driving circuit of an AC fan motor and more particularly to a driving circuit of an AC fan motor providing high voltage DC power to coils of the motor to increase the rotation rate of the motor.
2. Description of Related Art
With reference to FIG. 3, an AC motor (20) has two coils (La, Lb). The two coils (La, Lb) are connected in series and then connected to an AC power source (AC IN). Since AC power has a positive cycle and a negative cycle, shifting electromagnetic poles (N/S) are produced in the AC motor to drive and rotate the AC motor when AC power is input to the coils (La, Lb).
The AC motor has a low rotation rate and high power consumption, so a portion of the power will be converted to heat inside the AC motor when the AC motor is driven. Operational safety considerations mandate that an AC motor's casing not be made of plastic so the AC motor is heavy. In addition, the electromagnet cores and windings of the AC motor tend to be very large so the AC motor is not easy to miniaturize.
Therefore, the present invention provides a driving circuit to miniaturize the AC motor and make the AC motor have a high rotation rate and low power consumption.